School Of Architecture, Building and Design Bachelor of Science (Hons) in Architecture
Building Science II Project 1 Auditorium: A Case Study on Acoustic Design
Ang Averllen Foong Wing Hoe Ignatius Jee Shao Lang Tan Wui Xiang Tan Yik Ting Tan Yincy Yen Wei Zheng Yong Man Kit
Tutor: Mr. Azim Sulaiman
0321444 0320085 0320069 0321128 0325043 0318355 0320266 0319778
CONTENTS Topic 1.0 Introduction 1.1 Acknowledgement 1.2 Aim and Objectives 1.3 Historical Background 1.4 Site Information 1.5 Drawings
Page 1
2.0 Methodology 2.1 Measuring Instruments 2.2 Data Collection Methods 2.3 Sound Equipments 2.4 Equipments Specification
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3.0 Acoustical Phenomena 3.1 Acoustic in Architecture 3.2 Sound Intensity 3.3 Reverberation, Attenuation, Echoes and Sound Shadows 3.4 Issues of Acoustic Design Strategies 3.5 Acoustic Design for Auditorium
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4.0 Acoustical Analysis 4.1 Auditorium Design Analysis 4.2 Material and Properties 4.3 Acoustic Treatment and Components 4.4 Sound Sources 4.5 Noise Sources 4.6 Sound Propagation and Related Phenomena
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5.0 Reverberation Time
45
6.0 Observation, Recommendation and Conclusion
47
7.0 References
50
1.1 Acknowledgement
First and foremost, we would like to thank Mr. Azim for his guidance throughout this project that had helped us to improve our knowledge and understanding on the analysis of auditoriums. Besides, we would also like to thank Ar. Edwin that had given us a lecture which is helpful to our study. Last but not least, we are grateful to Mr. Nazrul, whom allowed us to conduct a site visit to the Cempaka Sari Auditorium, Putrajaya so that we were able to investigate and analyze the acoustic sound system present in the auditorium.
1.2 Aim and Objectives Acoustic design is one of the architectural and engineering techniques to control the behavior of sound in an enclosed space, which is an auditorium in this case. The purpose is to improve sound distribution in the enclosed space by enhancing the desired sound suited for the program. Acoustic design also aims to eliminate noise and undesired sound that would negatively affect the desirability of the sounds. For instance, specific measures will be taken to make sure the speech is more intelligible or to make music sound better for the users. Building materials, architectural designs and layouts of a space will be taken into consideration while engaging in acoustic designs.
1.3 Historical Background The auditorium Cempaka Sari is one of the landmark buildings along Persiaran Perdana. To the west sits the Grand Mosque and to the east across Persiaran Perdana, lays the Palace of Justice. The auditorium is connected to the Perbadanan Putrajaya Complex and it is a contemporary interpretation of traditional Islamic architecture. The auditorium is designed as a complex consists of low-rise medium sized buildings that are connected by pedestrian links with boutique retail spaces on the ground floor of each component. Auditorium Cempaka Sari is best suited for events such as exhibitions, meetings, product launch events, seminars and social events.
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1.4 Site Information Name of auditorium : Auditorium Cempaka Sari Location : Persiaran Perdana, Presint 3, 62100 Putrajaya, Malaysia Type of auditorium : Multi purpose auditorium Total volume : ~19000 mÂł Year of construction : 2012 Total seats : 610 fixed and cushioned
1.5 Drawings
Auditorium Plan Scale : NTS
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Second Floor Plan Scale : NTS
Third Floor Plan Scale : NTS
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Reflected Ceiling Plan Scale : NTS
Section Scale : NTS
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2.1 Measuring Instruments Digital Sound Level Meter
This device is used to measure the sound levels at a particular point within the auditorium. The unit of measure is decibels (dB) .It is commonly a hand-held instrument with a microphone and the diaphragm of the microphone responds to changes in air pressure caused by sound waves.
Measuring Devices
Measuring Tape
Laser Distance Measurer
These two devices are used to obtain the measurements of our chosen auditorium and to measure the distance of the sound level meter from the sound source when sound levels data were taken.
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Digital Camera A digital camera is used to document the existing context within our auditorium and aid on our analysis after the site visit. Images and videos were taken
as
evidence.
Smart Phone
Smart phone were used to play music in the auditorium that act as a sound source at a single point.
2.2 Data Collection Method To assure that the site visit could be carried out smoothly and without interruption, formal arrangements were made with the person in charge to make sure that the auditorium would be unoccupied, enabling us to conduct our investigation. We documented as many details as possible during the visit with the help of all the tools mentioned above along with all the necessary measurements required to assist our analysis.
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2.3 Sound Equipments
The surround system that Auditorium Cempaka Sari use is stereo system that allows panning and it adds depth to the acoustic image. This system is perfect to accomodate function such as speech reinforcement and greatly enhances live or pre-recorded music. The speakers is located at both side of the stage to give the best horizontal coverage that listeners are well covered by the pattern. Diagram 2.3.1 Sound Are Spreaded Into the Auditorium Uniformly
The speakers located at the highest position in the auditorium beside the stage facing the crowd to spread the sound uniformly to the whole area.
Diagram 2.3.2 The Speaker is Located at This Position to Ensure it Reaches its Maximum Effect
The subwoofer located at the staircase of the stage produce bass tones and low frequency tones at the left and right corners.
Diagram 2.3.3 The Subwoofer is Placed Beside The Stage
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2.4 Equipments Specification Product Brand
Sennheiser
Dimension
685 x 455mm
Power Consumption
1500 W RMS, 4 Ohms
Weight
67lbs
Frequency
45Hz-20kHz
Sound Level
96dB PRO X SUB L FL
Product Brand
Behringer
Dimension
640 x 400mm
Power Consumption
300W Constant, 1200W Peak
Weight
55.2lbs
Frequency
55Hz-18kHz
Sound Level
95dB
B1220 PRO
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3.1 Acoustics in Architecture Architectural acoustics is the study of the process of governing how both airborne and impact sound is transmitted and controlled within a building design. Every element within a room, from floor coverings to furniture affects the sound levels to some extent or another. The primary components that designers use to control sound are floor/ceiling assemblies, wall partitions and ceiling systems. Sound waves travel through many physical objects faster and with less loss of energy than they travel through air. Sound moves through building spaces most commonly through air, but the primary components can also transmit both airborne sound, such as human voices and music, and impact sounds, such as footsteps or doors opening. The size and shape of a room could also affect how sound waves travel as it determines how sound hits surfaces and the directions in which it is reflected.
3.2 Sound Intensity Sound intensity is defined as the sound power per unit area. The general context is the measurement of sound intensity in the air at a listener's location and the basic units are watts/m2 or watts/cm2. Many sound intensity measurements are made relative to a standard threshold of hearing intensity I0, which is
However, sound intensity levels are quoted in decibels (dB) much more often than sound intensities in watts per meter squared. Decibels are the unit of choice in the scientific literature as well as in the popular media. The reasons for this choice of units are related to how we perceive sounds. How our ears perceive sound can be more accurately described by the logarithm of the intensity rather than directly to the intensity. The sound intensity level β in decibels of a sound having an intensity I in watts per meter squared is defined to be
where I0 = 10−12 W/m2 is a reference intensity. I0 is the lowest or threshold intensity of sound a person with normal hearing can perceive at a frequency of 1000 Hz. Sound intensity level is not the same as intensity. Because β is defined in terms of a ratio, it is a unitless quantity. The units of decibels (dB) are used to indicate this ratio is multiplied by 10.
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C F B
E D
A
Positions
Silent (dB)
Talking (dB)
A
23
68
B
26
70
C
22
67
D
27
73
E
32
75
F
37
74
Sound Data Collection Table
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3.3 Reverberation, Attenuation, Echoes and Sound Shadows Reverberation is the collection of reflected sounds from the surfaces in an enclosure like an auditorium. It is a desirable property of auditoriums to the extent that it helps to overcome the inverse square law dropoff of sound intensity in the enclosure. Hard surfaced rooms normally will have a longer reverberation time than rooms finished with sound absorbing materials. When a sound wave travels outward in all directions and encounters an obstacle such as a wall, floor or ceiling surface the direction of the sound will be changed or reflected. The direction of travel of the reflected sound will be at the same angle as the original sound striking the surface. However, if it is excessive, it makes the sounds run together with loss of articulation and the sound would become muddy and garbled. When sound travels through a medium, its intensity diminishes with distance. This weakening in the energy of the wave results from two fundamental causes, scattering and absorption. Scattering is the reflection of sound in directions other than its original direction of propagation. Absorption is the conversion of sound energy to other forms of energy. The combined effect of scattering and absorption is called attenuation.
An acoustic shadow or sound shadow is a phenomenon caused by the absorption or obstruction of sound wave by an object in its path. The effect produced is perceived as a reduction in loudness depending on the observer's position concerning the sound source and obstructing object and is greatest when the three are aligned. High frequencies are more easily absorbed than lower ones and are less susceptible to diffraction, where they move less easily around objects because of their short wavelengths. Therefore, the attenuation of high frequencies is noted in a sound shadow. More reflected sound from the environment is also likely to be received than direct sound.
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3.4 Issues of Acoustic Design Strategies Acoustical conditions in an enclosed space are achieved when there is clarity of sound in every part of the occupied space. The sound should increase to a suitable intensity everywhere with no echoes or distortion of the original sound with a correct reverberation time. Thus, these acoustical deficiencies in buildings are essential to be identified, diagnosed and rectified. To distribute the sound evenly and to avoid areas where the sound quality is either weak, too excessive or cannot be heard clearly, acoustical reflectors or diffusers are implemented. Reflectors and diffusers are used to adequately reduce interfering reflections in any one direction by spreading the sound more evenly across the space. Besides that, acoustic diffusion or sound reflection serves to accommodate a broader sound coverage for speech and music and is often used to enhance speech intelligibility and clarity in assembly halls, auditoriums, recording studios, theaters and classroom.
3.5 Acoustic Design for Auditorium Selection of the Site Before construction the first significant factor to be considered is the location. The proposed site should be as far away as possible from noisy places, like railway tracks, highways, industrial areas and airports for excellent acoustical quality of the hall.
Volume The size of the hall should remain optimum, as small halls would cause uneven distribution of sound due to the formation of stationary waves while overly large halls would create longer reverberation time that would result in confusion and unpleasant sound.
Shape and Form Instead of parallel walls, spade walls are preferred and curved surfaces should be built with proper care to produce a concentration of sound in a particular precinct. Great planning is also a necessity to assure the reduction of echoes.
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Use of Absorbents The use of absorbents is imperative and a common strategy in auditorium design as the use of proper absorbent material enhances the quality of sound. They are often used on the rear wall of the auditorium, as well as the ceiling, as the reflection sound that occurs around these areas are of no good.
Reverberation Reverberation time must be controlled to a perfect balance (0.5 seconds for auditoriums, 1.2 seconds for concert halls and 3 seconds for theatres). If reverberation time is low, the intensity will be weak while if high, the sound will be unpleasant. The proper use of absorbent materials, types of furniture used, the presence of open windows and the capacity of the audience are all the key components that affect the reverberation time.
Echelon Effect The regular intervals spacing of reflecting surfaces between staircase and sets of hand railings may produce repeated echoes and this disturbs the quality of the original sounds produced. So, thick carpeting and wide gaps between stairs are generally preferred.
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4.1 AUDITORIUM DESIGN 4.1.1 Shape and Massing The horseshoe shaped auditorium ensure good visibility, a sense of proximity to the sound source and mutual eye contact between the spectators. The geometry of the auditorium determines some gaps due to a concentration of the early sound reflections on the back of the room, involving the last rows of seats, thus causing a non-uniform spread of sound in the auditorium. This concentration of reflections does not create optimal conditions for good acoustics due to excessive reverberation and negative influence on the listening to music performances.
Diagram 4.1.1 Expected sound path of Auditorium Cempaka Sari
4.1.2 Volume The ceiling height is about the one-third of the room width which is determined by the overall room volume. The volume influences both reverberance and loudness.
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4.1.3 Levelling of Seats and Stage Raked seats and raised stage are in the most effective configuration that defines the relationship between the speaker on stage and the audience. This arrangement of seats allow the occupants in the furthest-most seats to hear clearly. This is possible due to the effectiveness of the sound waves reaching the ears of the occupants when uninterrupted by any objects blocking or absorbing it.
Diagram 4.1.2 Levelling of seats and stage used by Auditorium Cempaka Sari. This ensures optimal sound travel to all audience. Elevated source arrangement reduce SIL loss.
4.1.4 Arrangement of seats The seat arrangement within the auditorium is a hybrid configuration which are fan shaped and end stage. This ensures a maximum number of seats are fitted, and obtain an optimum sightline to stage area from every seat. As spherical wavefront will be formed when sound emits from the source, this layout helps to achieve the most effective acoustic quality as all seats fall within the angle of the existing sound projection area.
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Diagram 4.1.3 Existing sound source with optimum 140 degrees wide layout ensure high frequency sounds are able to be discerned.
4.1.5 Layout of boundary surface The hybrid configuration of convex shaped and stepped ceiling that aids in reflecting the sound back towards the seating area and increasing the volume of the sound as it reaches the ears of the occupants. The convex shaped ceiling scatter the sound to the middle and back part of auditorium. As the ceiling is parallel to the floor, a little flutter echoes are being noted on stage.
Diagram 4.1.4 Expected sound reflection from ceiling of Auditorium Cempaka Sari to all audience.
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4.2 Material and Properties The Cempaka Sari Auditorium uses a wide variety of components and materials to produce the acoustic environment it currently has.
Diagram 4.2.1 Section of the auditorium showing materials and components used.
The materials can be divided into absorbent or reflector, depending on their Noise Reduction Coefficient (NRC) rating, where the most reflective is 0 and the most absorbent is 1. In order to achieve the desired level of reverberation time, designers have to balance their choice of materials, and using the NRC ratings, calculate the reverberation time.
Diagram 4.2.2 Plan of the auditorium showing the floor materials..
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4.2.1 Interior Material Noise Reduction Coefficient Building Component
Flooring
Material
Timber
Surface Finishers
Veneer
Coefficient 125Hz
500Hz
2000Hz
0.18
0.42
0.83
Nylon Carpet Wall
0.60
Granite
Uneven Surface
0.01
0.02
0.03
Timber
Laminated
0.18
0.42
0.83
Ceiling
Battens
Gypsum Plasterboard
0.29
0.05
0.07
Stairs
Timber
Laminated
0.18
0.42
0.83
Nylon Carpet
0.60
Seating
Timber and Fabric
-
0.13
0.59
0.61
Door
Timber
Laminated
0.14
0.06
0.10
Curtain
Velour
0.03
0.15
0.5
Partitions
Timber
Laminated
0.18
0.42
0.83
Acoustic Panel
Perforated Veneer Chipboard
Laminated
0.41
0.58
0.68
Porous Fibre
-
0.85
0.80
0.90
Cotton Felt
Muslin Fabric
0.15
0.70
0.95
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4.2.2 Exterior Material Noise Reduction Coefficient Building Component
External Facade Cladding
Material
Stainless Steel
Surface Finishers
Polished
Coefficient 125Hz
500Hz
2000Hz
0.35
0.44
0.54
4.2.3 Misc. Item Noise Reduction Coefficient Building Component
Material
Surface Finishers
Coefficient 125Hz
500Hz
2000Hz
Air
-
-
-
-
0.007
Human
-
-
0.21
0.46
0.51
Ventillation Grille
Aluminium
Powder Coated
0.6
0.6
0.6
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4.3 Acoustic Treatment and Component Auditorium Cempaka Sari is best suited for events such as exhibitions, meetings, product launch events, seminars, social events etc. Loud music performance or concert is not so suitable because the acoustic quality of this auditorium caters well to talks. The equipment installed in the auditorium along with the selected material provide better acoustic experience to speech giving or even enhance the volume with a microphone.
4.3.1 Stage Flooring i. Timber Veneer Flooring The choice of using timber as the stage’s flooring varies. For structural and aesthetic purpose, this type of flooring is generally much more stable and durable. While solid wood can be prone to warping and splitting, veneer is made of layers of thin wood glued together, the chance for splitting or cracking is reduced. Furthermore, the glue provides additional strength, resulting it to be stronger than natural wood. Not to mention its natural tendency to reflect sound.
Diagram 4.3.1.1 Timber veneer flooring of stage
Diagram 4.3.1.2 Close up of veneer flooring
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ii. Nylon Carpet Flooring Nylon carpet fiber is a well-known synthetic carpet fiber that is considered the most durable. Manufacturer today is able to produce the carpets in thinner, finer strands, considering softness is a big factor for sound absorbent.
Nylon carpet flooring in the auditorium prevents hard contact with the floor, although of no help against airborne sound transmission, it at least diminished impact sounds. The noise reduction coefficient for typical commercial carpets is around 0.60.
Diagram 4.3.1.3 Floor carpet
Diagram 4.3.1.4 Stage carpet
Diagram 4.3.1.5 Comparison of surface
Diagram 4.3.1.6 Subwoofer on carpet
The vibration of the bass playing subwoofer placed on the floor compared to hard finish flooring, reducing the direct impact from transferring to the floor structure.
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4.3.2 Wall i. Granite (w/ uneven surface) Granite wall has very low absorption, good for reflecting acoustic sound. Though it has a rough and uneven surface so that the sound reflected are dispersed instead of directly reflected. Installed on both rear of the auditorium’s interior, they help traject the sound wave from the speaker to the audience. The granite panels have a thermal finish.
Diagram 4.3.2.2 granite surface
Diagram 4.3.2.1 granite wall panels
ii. Timber Veneer Part of the walls in the auditorium uses the same material as the floor. The continuous use of timber veneer is repeated at the wall near the stage.
Diagram 4.3.2.3 timber veneer wall
Diagram 4.3.2.4 timber veneer casing
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4.3.3 Ceiling i. Gypsum Plasterboard Ceiling The ceiling profile of Cempaka Sari has both curved edge and plane surface, to help reflect and disperse sound wave to the audience. The gypsum plasterboard installed on battens allow different wavelengths of sound to be reflected at various position which improves the acoustic intimacy, clarity, and strength of the overall room’s sound.
The ceiling is plastered with a thicker gypsum board to resist any vibration. Other properties of gypsum board includes lightweight material and also fire resistance.
Diagram 4.3.3.1 Plastered ceiling
Diagram 4.3.3.2 Auditorium ceiling profile
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4.3.4 Stairs i. Timber with Nylon Carpet The steps at the aisle of the auditorium are entirely covered with nylon carpet to reduce the noise produced by footsteps. Carpet is an excellent sound absorptive material. This particullar material can perform dual role of floor covering and versatile acoustical aid. Carpet can also helps decrease the risk of airborne noise transferring to the neighbouring floor.
Diagram 4.3.4.1 Nylon carpet stairs
Diagram 4.3.4.2 Nylon carpet aisle
Nylon carpet Acoustic underlay Acoustic mineral wool Fixing batten 30mm acoustic plaster board
Diagram 4.3.4.3 Carpet stairs section detail
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4.3.5 Seating i. Timber Structure with Fabric Cushion The Cempaka Sari Auditorium uses timber upholstered chairs for its seating. The cushion of the chair not only provides comfort, it also serves well as an sound absorbent, which can help reduce the reverberation time in the auditorium.
Diagram 4.3.5.1 Upholstered tip-up chair
Diagram 4.3.5.2 Upholstered tip-up chair overview
It adds to the acoustical absorption of an empty auditorium and allows the space to achieve a similar quality of sound whether the auditorium is filled to partial or maximum capacity. A solid, hard material changes
the
acoustic
performance
of
the
auditorium depending on the number of occupants and the reflected sound vibrations.
Diagram 4.3.5.3 Location of upholstered chair on plan
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4.3.6 Door i. Solid Timber Door The door located right beside the VIP aisle is made entirely out of timber. While the door does not have any fancy soundproofing component, it is still extremely functional in term of acoustic insulation, as a solid chunk of timber is naturally good at reflecting sound waves. However, the door seems to create squeaky noises when opening/closing, and can thus create interruption in the acoustic environment.
Diagram 4.3.6.1 Solid Timber Door beside VIP aisle
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4.3.7 Curtain i. Cotton Velour Curtain Velour curtains can dramatically reduce high frequency echo and excessive reverb in a room. Velour curtains primarily intended for sound absorption need to be as heavy as possible with 75% - 100% fullness. Adding extra layers through double facing or lining will provide additional sound dampening. The heavier the finished curtain, the better the sound absorption. The two key factors in sound absorption are mass and air space.
Diagram 4.3.7.1 Double layer curtain damping the sound wave
The air space decouples the layers of mass. Increasing the thickness(mass) of the curtain will have some effect, but less of an effect than increasing the air space. The biggest initial gain in sound absorption comes by creating the air space to begin with.
Cotton fabrics tend to perform slightly better than synthetics due to the added mass. This highly porous textile act as thousands of tiny sound traps, which capture and absorbs the energy. The pleated curtain expose more surface area for sound absorption to occur, hence, providing a better acoustic performance.
Diagram 4.3.7.1 Double layer curtain
Diagram 4.3.7.2 Pleated cotton curtain
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4.3.8 Partitions i. Timber partitions with acoustic panels The VIP Area is surrounded by timber partitions to distinguish itself amongst the rest. The partitions are made out of timber panels with timber structures, with nothing but void in it. Because of that, when the occupants accidentally hit the partition, it can create a loud noise, which can be extremely disruptive. To counteract that, the partitions are installed with fabric acoustic panels, which can help reduce the impact. Not only that, the acoustic panels also help reduce the echo in the small echo chamber which is the VIP area.
Figure 4.3.1 The VIP Area in Cempaka Sari Auditorium
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4.3.9 Acoustic Panels i. Timber Perforated Acoustic panels Perforated panels are the most economical way to get an acoustic treatment with a high degree of absorption. It comes in various pattern and hole diameter, different intensity in sound absorption and aesthetic results can be achieved. The acoustic material absorbs or dampen the sound waves that emits from stage. Generally, the idea is to prevent the sounds from echoing off the walls of an enclosed space. If this issue is left unchecked, it would leave the audience with a confusing experience. Mostly used as acoustic correction, applicable to walls and ceilings, but in this case the auditorium had the installations with exposed covering on the walls in lacquered surface finishes.
● ● ● ●
Features HOLE DIAMETER: 34mm SPACING: 115x117mm align PERFORATED SURFACE: 3.4% THICKNESS: 12mm/16mm
Diagram 4.3.9.1 Timber Perforated Panels
34mm Diameter hole opening
10mm Acoustic plasterboard
Timber Perforated Panel
10mm Mineral wool insulation
Air cavity
15mm Barricade noise barrier
5mm Acoustic fabric
10mm Gypsum board
Diagram 4.3.9.2 Acoustic panel section detail
Diagram 4.3.9.3 Construction Detail of Timber Perforated Panels (example)
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ii. Muslin Fabric with Cotton Felt The sound absorption panels can be found at the VIP entrance, as well as the on the partitions of the VIP area. The placement of the panels is to absorb the sound produce from the people walking up and down the stairs beside the VIP area. Preventing disruption from footsteps and squeaky noise produce by the loose timber floor panel. Besides that, the acoustic panel also help absorb noise from outside coming in through the doorway, as well as the squeaky noise produce by the door itself.
Diagram 4.3.9.4 Acoustic panel around the entrance
Diagram 4.3.9.5 Muslin fabric material texture
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4.3.10 Exterior Facade i. Double Sheet Stainless Steel Skin The exterior of the auditorium is cladded with polished stainless steel. The stainless steel cladding serves as a primary insulator against noise pollution from the exterior environment. However, due to the lack of thickness of the steel plate used, the steel plates might absorb sound waves and proceed to vibrate, which can contribute to the noise pollution.
Diagram 4.3.10.1 Stainless Steel Cladding
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4.3.11 Ventilation Grille i. Powder Coated Aluminium Grille The Cempaka Sari Auditorium consists of four ventillation grilles. The openings of ventilation grilles allow sound waves to escape or enter the auditorium, and thus it is best installed high up on the wall.
Diagram 4.3.11.1 Ventilation Grill
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4.4 External Noise The external noise that affect the user experience in the auditorium is the event that located at entrance downstairs. The event uses sound amplifier devices to amplify the voices hence create noises penetrate into the auditorium
Diagram 4.4.1 The Event At Ground Floor That Create Noise
The lobby of the auditorium before entering the spaces has sitting area and people would gather around it creates some external noises as well.
Diagram 4.4.2 The Lobby Before Entering Auditorium
As the Cempaka Sari Auditorium is located beside of the main road which is Jalan Persiaran Perdana causes it to create sound pollution and affect the event in the building itself.
Diagram 4.4.3 Highlighting The Road That In Front of Auditorium
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4.5 Internal Noise The internal noises that can be found in the auditorium hall is the stage, because of flooring material factors that it made from wood.
Diagram 4.5.1 Highlighting The Stage
The next internal noises is is that the wall of the backstage is made out of pure concrete without any other absorbent material.
Diagram 4.5.2 Highlighting The Back Stage
The VIP entrance or sitting area of the auditorium is also one of the internal noises because of its wooden flooring. While the VIP enters the lounge sitting area it will create noises as they are secondary entrance at the sitting area which direct the external noises in there
Diagram 4.5.3 Highlighting The Entrance To The VIP Area
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Air-conditioning at the ceiling create noises when its switch on at full fan speed. As the sizes of the auditorium is huge so the circulation of air flow by constantly changing the freshness of air is very important hence the air-conditioning is one of the main internal noises. Diagram 4.5.3 Air Conditioning Vents
Air blower located at the end of the stage to help circulate the air is also one of the noise contributor to the space.
Diagram 4.5.4 Portable Air Blower
Anti-slip rubber at the edge of the staircase caused noise when it is stepped on. Woman shoes especially high heels would contribute to more noise.
Diagram 4.5.5 Anti-slip rubber
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4.6 Sound Propagations and Related Phenomena The measurement of the auditorium from a fixed sound source, outputting a constant 500Hz at 80dB, has resulted in the following findings: 1. 2. 3.
The auditorium’s form has severely affects the clarity of sounds at certain spaces. The back seats receives multiple sound reflections. The auditorium receives excessive reverbs, affecting the speech intelligibility.
4.6.1 Sound Concentration The sound concentration zone of the auditorium can be determined through the measurement of the sound intensity level (SIL) from the sound source. There is a distinct sound concentration at the back of the auditorium.
Diagram 4.6.1 SIL measurement of the auditorium
The varies in sound concentration causes by the horseshoe form of the auditorium, resulting in an early sound reflections on the back of the room and thus, created a non-uniform spread of sound in the auditorium.
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Diagram 4.6.2 Sound Reflection Diagram. The detrimental design of the auditorium reflecting the sound path towards the back seats.
The sound concentration zone is created through the auditorium’s horseshoe form. Insufficient usage of sound absorbent materials at the back of auditorium has caused the sound to be concentrated in the back seats.
Absorbant Absorbancy coefficient at 500Hz > 0.1 Reflective Absorbancy coefficient at 500Hz < 0.1 Diagram 4.6.3 Sound Reflection Diagram with materials.
The authorities has taken steps to reduce the impact of sound concentration in the auditorium through the implement of timber perforated acoustic panels at the sides. The rear concrete facade causes large amount of sound reflection at the back seats.
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4.6.2 Sound Reflections The sound is reflected back towards the audience in order to increase the acoustic quality of the auditorium. However, the added design of reflection and the amount of these reflection must be controlled to minimize the sound defection by echoes.
The plasterboard ceiling functions effectively to reflect the sound back to the audience. Nonetheless, the auditorium floor has to be covered with absorbent materials to minimize the resultant reflected sound to ensure clarity of sound transmission.
Absorbant Absorbancy coefficient at 500Hz > 0.1 Reflective Absorbancy coefficient at 500Hz < 0.1 Diagram 4.6.4 Sound propagation towards individual at Row 3, proving the lack of reflected sounds.
Absorbant Absorbancy coefficient at 500Hz > 0.1 Reflective Absorbancy coefficient at 500Hz < 0.1 Diagram 4.6.5 Sound propagation towards individual at Row 8, proving adequate sound reflection to the vip seats.
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The authority has implemented a combination of absorbent materials onto the auditorium’s flooring and facade to create a rich soundscape. However, the concrete rear facade has resulted in excessive sound reflection at the back seats, severely obstructing the audience’s experience.
Absorbant Absorbancy coefficient at 500Hz > 0.1 Reflective Absorbancy coefficient at 500Hz < 0.1 Diagram 4.6.6 Sound propagation towards individual at Row 16, proving excessive sound reflection to the back seats.
4.6.3 Echoes and Sound Delay Echoes are the distinctive repetition of the original sound whereas a reverberation is perceived when the reflected sound wave reaches subject’s ear in less than 0.1 second after the original sound wave.
In an auditorium, the reflective surface plays the major role as an effective source of sound delay. In Cempaka Sari auditorium, sound delay of 40ms and above will be considered as an
12.2m
12.6m
echo as it is an auditorium catering for speech.
6.2m Time Delay = (12.6+12.2-6.2)/0.34 =54.7ms
Diagram 4.6.7 A time delay of 54.7ms towards row 3 exceeded the optimum sound delay for a speech auditorium.
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16
.0m
.0m
11 15.8m d n t Sou Direc
Time Delay = (16.0+11.0-15.8)/0.34 =32.9ms
Diagram 4.6.8 A time delay of 32.9ms towards row 8 is acceptable for a speech-oriented auditorium.
Direct Sound
7.8
m
.7m 25
m 30.1 nd u ct So e r i D
Time Delay = (25.7+7.8-30.1)/0.34 =10.0ms
Diagram 4.6.9 A time delay of 10.0ms towards row 16 is acceptable for a speech-oriented auditorium.
In conclusion, the sound delay in the VIP area and the back seats are optimum and suitable for the use of speech. The front seats may suffer intelligible sound caused by the echoes as it has a sound delay higher than the optimum level of 40ms.
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5.0 Reverberation Time Calculation The reverberation in Cempaka Sari auditorium is considered as excessive as the desirable reverberation for an auditorium falls between 1.4 to 2.0. The reverberation time of Cempaka Sari is 2.16 seconds, which is not conducive for good speech intelligibility.
Diagram 4.6.10 Surface Absorption of materials implemented in Cempaka Sari Auditorium
Surface Absorption Perforated Acoustic Panels =351.4m2 x 0.80 =281.12m2 sabins
Curtain =273.5m2 x 0.50 =136.75m2 sabins
Carpet =1336m2 x 0.60 =801.60m2 sabins
Fabric Chairs = 318.8m2 x 0.59 =188.10m2 sabins
Total absorption of room surface = (281.12 + 801.60 +136.75+188.10) = 1407.57m2 sabins
19000m3
Reverberation Time =0.16(19000m3 )/1407.57m2 sabins = 2.16seconds
Diagram 4.6.11 Reverberation time of Cempaka Sari Auditorium.
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6.1 Observations Based on our analysis and calculation, the auditorium has an high reverberation time, which create echoes that is more suitable for musical performance, rather than speeches and talks. Besides that, opening and closing of the doors can be a disruption to the environment due to the squeaky noise that are created. In addition to that, the uncarpeted timber floors in the auditorium creates loud footstep noises when walked on.
Despite all the issues, the auditorium does have a few good side about it. For example, sounds can be heard loud and clear throughout the entire auditorium, even without the use of microphones. The auditorium is also very welly soundproofed, with thick concave walls surrounding the space as well as sealed door, both helps prevent sound waves from going out of the interior space, and vice versa.
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6.2 Recommendations
Maintenance
More absorbent
Scheduled maintenance, to fix loose screw and
The Cempaka Sari Auditorium can benefit from
bolt, greasing door hinge and handle to
installing more absorbent materials such to
prevent unwanted noise that would affect or
reduce the reverberation time to a much more
disturb the auditoriumâ&#x20AC;&#x2122;s acoustic experience.
desirable length.
Air-conditioning
Replacing old carpets
Provide sufficient air conditioning or better
Replace and refurbish the auditorium with
ventilation to avoid using portable ventilation
new carpets that are softer and with better
system, which may perform poorly and
enhanced synthetic material as it could help to
produce loud noise.
improve the acoustic issue. Better absorption of sound to cancel the echoes.
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7.0 References ● ● ● ●
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Sound Intensity (n.d.). Retrieved September 29, 2017, from http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/intens.html Learning, L. (n.d.) Sound Intensity and Sound Level. Retrieved September 29, 2017, from https://courses.lumenlearning.com/physics/chapter/17-3-sound-intensity-and-sound-level/ Sound Shadow (n.d.). Retrieved September 29, 2017, from https://www.sfu.ca/sonic-studio/handbook/Sound_Shadow.html State the acoustic requirement of good auditorium. Explain how these requirements can be achieved. (1968, November 01). Retrieved September 29, 2017, from http://www.ques10.com/p/10237/state-the-acoustic-requirement-of-good-auditoriu-1/ Auditorium Cempaka Sari. (n.d.). Retrieved October 02, 2017, from https://10times.com/venues/auditorium-cempaka-sari Guinness World Records 2017. (n.d.). Retrieved October 02, 2017, from https://books.google.com.my/books?id=hxAyDQAAQBAJ&pg=PA255&lpg=PA255&dq=auditori um%2Bcempaka%2Bsari%2BHISTORICAL%2BBACKGROUND&source=bl&ots=wuag5ohez0&sig= y0ljw61inddzoWu0iNluKH-C2Rc&hl=en&sa=X&redir_esc=y#v=onepage&q=auditorium%20cem paka%20sari%20HISTORICAL%20BACKGROUND&f=false Auditorium Acoustics and Architectural Design. (n.d.). Retrieved October 02, 2017, from https://books.google.com.my/books?id=InKLAgAAQBAJ&pg=PA20&lpg=PA20&dq=sound%2Bpr opagation%2BIN%2BAUDITORIUM&source=bl&ots=4xdxMDBNZ7&sig=s8h1dwAcjJSzjmZ-M-98 PHvnCVY&hl=en&sa=X&redir_esc=y#v=onepage&q=sound%20propagation%20IN%20AUDITOR IUM&f=false Acoustic Physics in the Theater. (2017, May 22). Retrieved October 02, 2017, from https://www.octaneseating.com/acoustic-physics-in-the-theater The acoustical design of the new lecture auditorium, Faculty of Law, Ain Shams University. (2012, June 29). Retrieved October 02, 2017, from http://www.sciencedirect.com/science/article/pii/S2090447912000317 (n.d.). Retrieved October 02, 2017, from https://www.music.mcgill.ca/~gary/307/week3/rooms.html Lecture 4- Auditorium Design & Sound Reinforcement Mansha. (n.d.). Retrieved October 02, 2017, from https://www.scribd.com/document/339941127/Lecture-4-Auditorium-Design-Sound-Reinforce ment-Mansha Barron, M. (n.d.). Auditorium acoustics and architectural design. Retrieved October 02, 2017, from https://capitadiscovery.co.uk/derby-ac/items/518057 Improving Sound in Your Auditorium. (n.d.). Retrieved October 02, 2017, from http://www.christianschoolproducts.com/articles/2008-November/Feature-Articles/Improving -Sound-in-Your-Auditorium.htm
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